The present invention relates to a resin composition containing a modified polyphenylene oxide and having excellent heat resistance, mechanical property, impact resistance, solvent resistance (especially resistance to hydrocarbons) and transparency.
Polyphenylene oxide (hereinafter referred to as "PPO") is a resin having excellent heat resistance and mechanical and electric characteristics, but in some uses it is sufficient in impact resistance, processability, solvent resistance and antioxidation property.
In order to eliminate the above defects, it is proposed in U.S. Pat. No. 3,383,435 to blend PPO with polystyrene or a modified polystyrene. The blend has improved impact resistance, processability and antioxidation property, but this technique is insufficient for improving the solvent resistance.
The solvent resistance of PPO can be improved by blending PPO with an acrylonitrile-styrene polymer (AS resin) or an acrylonitrile-butadiene-styrene polymer (ABS resin) instead of polystyrene or the modified polystyrene. However, the impact resistance and the mechanical property are lowered and the antioxidation property is not improved. This fact indicates that PPO is poor in compatibility with the AS resin or ABS resin and mere blending does not provide an available resin composition. The antioxidation property is not improved so far as PPO is blended with a resin incompatible therewith. If the AS resin or ABS resin would be compatible with PPO, mechanical properties such as tensile strength and toughness, impact resistance and other properties that the AS resin or ABS resin stands at advantage over polystyrene or a high impact polystyrene, would be improved as well as the solvent resistance. However, it is understood that PPO and the AS resin are not compatible, from the fact that if they are admixed, the mixture becomes opaque. For instance, if each of an AS resin containing about 5% by weight of acrylonitrile and PPO is dissolved in an equal amount of cloroform and a casting film is prepared from the mixture thereof, the film is opaque. Also, if a casting film is prepared in the same manner as above by employing an AS resin having an acrylonitrile content of about 20% by weight, the surface becomes very rough and no film is prepared. Even if PPO is blended with an AS resin having an acrylonitrile content of less than 5% by weight, marked improvement in solvent resistance is not expected.
Graft polymerization of an AS resin onto PPO is available for raising the compatibility of PPO with AS resin or ABS resin to provide a practical resin composition of PPO and the AS resin or ABS resin.
A graft polymerization technique of acrylonitrile onto PPO is disclosed in Japanese Examined Patent Publication (Tokkyo Kokoku) No. 41383/1971. This publication proposes an anionic graft polymerization using an alkali metal. In case of employing monomers, e.g. styrene and acrylonitrile, which are largely different in electronegativity from each other, it is difficult to prepare a random graft copolymer by an anionic graft polymerization. Therefore, a modified PPO as obtained by grafting an acrylonitrile-styrene copolymer onto PPO according to this technique, namely acrylonitrile-styrene grafted polyphenylene oxide (hereinafter referred to as "ASGPPO"), is not compatible with industrially used usual AS resins. Japanese Unexamined Patent Publication (Tokkyo Kokai) No. 115260/1975 and No. 137130/1980 propose blending of a modified PPO prepared by graft polymerization of an AS resin onto PPO with an AS resin. These ASGPPO resins are in a uniform dispersion state as shown in FIG. 1 of the Japanese Publication No. 137130/1980, and the PPO portion and the AS resin portion are not compatible with each other. Even if the ASGPPO resin is blended with AS resin, no transparent resin composition is obtained. In that case, two loss peaks derived from the respective components are observed in dynamic mechanical measurement.
It is an object of the present invention to improve the solvent resistance, antioxidation property and impact resistance of PPO without impairing excellent characteristics of PPO such as heat resistance, mechanical property and electric characteristics.
A further object of the invention is to provide a resin composition containing a modified PPO.
A still further object of the invention is to provide a resin composition having excellent solvent resistance, antioxidation property, impact resistance, heat resistance, mechanical property, electric characteristics and transparency.
These and other objects of the present invention will become apparent from the description hereinafter.